Traditionally, communications systems have offered services to their users by using monolithic service servers. The term monolithic server refers to a kind of apparatus comprising processing and data storage capabilities that allows it to process the signaling it can receive, as well as the signaling to be sent, by using data it stores internally. In other words, a monolithic server is arranged to serve a certain service by using its internal processing means and by using the data it stores internally.
However, factors such as scalability, and performance or deployment/implementation costs, are starting to drive towards another kind of solution, wherein the functionality provided by some monolithic servers is—say—“tiered” resulting into a layered architecture. The principle behind this kind of solution (hereinafter also referred as “data layered architecture”, DLA) consists on decoupling, along different servers, the service logic processing functions from the mere data storage functions.
A data layered architecture, DLA, is a physical infrastructure that comprises, en essence: a database server (DBS) acting as a back-end storage system, and a plurality of servers which access the DBS for obtaining and/or modifying data stored therein so as to provide the services they respectively serve. Depending on factors, such as: the amount of data to be stored, the required access availability, data distribution/replication policies, etc; the DBS can comprise one database, or a plurality of databases (e.g. implemented along separated machines). In any case, the principle of decoupling the service logic processing from the mere data storage allows using commercially available robust DBS products, which can act as a reliable back-end storage in DLA implementations, rather than devising costly proprietary (monolithic) products having to cope with, both: high message signaling processing capabilities for processing the service(s) they serve according to the specific service(s) logic, and high capacity/resiliency in what regards to data storage capabilities.
Moreover, since the same DBS can be used as a back-end data storage for a plurality of service servers serving the same or different services, the total signaling due to a particular service in a communications system can e.g. be distributed along a plurality of similar service servers adapted for serving said particular service and adapted also to DLA architecture (e.g. using any suitable load balancing mechanism), which should then act as signaling/processing front-ends. This allows reducing even more the cost for producing and/or maintaining such a kind of servers, since the processing load per server can be diminished, as the total signaling due to a certain service can be divided among the available (front-end) servers. Furthermore, this provides also scalability advantages for the operator of a communications system, since it can adjust the number of (DLA adapted) service servers according to the signaling demands for a given service and, thus, reduce its operational and capital expenditures.
Accordingly, the service servers which are more likely envisaged to be adapted according to a DLA are those that, given the specific characteristics of the service(s) they serve, have to stand with a high rate of signaling messages, and/or that are required to handle a huge number of data, so as to provide said service(s). The cost for producing and/or maintaining these servers can thus be reduced, since their complexity can be diminished, as they are not required to have high processing capabilities and, at the same time, high storage capabilities.
Examples of service servers which are envisaged to be adapted according to a DLA are, among other: Home Location Registers (HLR), Home Subscriber Servers (HSS). Other kind of servers can be, for example, servers providing (e.g. through web browsers) a plurality of users with web-based applications such as: calendar services, bank/financial services, personalized data storage services, etc; wherein the data they need for their service operation relating to the served users are stored in a back-end storage system (DBS).
For example, a HLR server adapted to a DLA architecture can then comprise signaling and processing means for processing e.g. Mobile Application Part (MAP) messages to/from Mobile Switching Centers/Visitor Location Registers (MSC/VLRs) or Serving GPRS Support Nodes (SGSNs), whilst the data it would need for such a processing (e.g. user's data of a user relating to circuit-switch CS and/or packet-switch PS domains for the concerned user/s, such as: user and/or terminal identifiers, location information, supplementary service data, service barring data, etc) should be accessed from a back end DBS, which could also store data of other kind of service servers (e.g. HSSs, web servers, authorization/authentication AAA servers, etc). Similarly, for example, a HSS server adapted to DLA can comprise signaling and processing means for processing e.g. DIAMETER (IETF RFC 3588) signaling to/from Call Session Control functions (CSCFs) and Session Initiation Protocol SIP Application Servers (ASs), whilst the data it would need for such a processing (e.g. the so called “User Profile” data for the concerned user/s) in relationship with IP Multimedia domain IMS could be accessed from the same back end DBS as the one used by HLR servers, or other kind of service servers.
A further advantage of DLA is that, in a communications system comprising a number of service servers providing services to a plurality of users, it is not required all these servers to be adapted to DLA features, but only some of them. For example, in case of a communication system comprising an IP Multimedia domain (IMS), HSS servers of the system can be adapted to DLA, whilst CSCFs (and/or AASSs in some cases) can continue being—say—“monolithic” service servers handling (i.e. storing and accessing for use) locally the data they need to use for providing their respective service. Similarly, in case of a mobile communication system comprising e.g. GSM circuit-switch CS and/or packet-switch PS domains (GSM/GPRS), HLR servers of the system can be adapted to DLA, whilst other service servers, such as MSC/VLRs, SGSNs, etc continue being “monolithic” in the same sense as described above.
It is to be noticed that service servers such as: CSCFs, MSC/VLRs or SGSNs, handle data of a given user on a temporary basis (i.e. locally store and use data of some users while these users are registered and served through them). As opposed, other service servers, such as HSSs, HLRs, or other kind of subscriber servers, are intended to hold on a permanent basis the—say—master copy of some of these data (i.e. data held locally and temporarily on CSCFs, MSC/VLRs, etc), as well as data related to other users (e.g. not registered users), either: stored locally (i.e. in monolithic implementations), or accessed in a back-end DBS. This circumstance (i.e. temporary handlers of data versus master handlers) can also appear in other kind of communications systems, which can also benefit of adapting accordingly at least part of its network infrastructure to DLA.
When coming to data provisioning, DLA might also offer further advantages. For example, in a system comprising only monolithic service servers, when some data related to a user is/are to be modified (e.g.: initially set, altered its current content, or deleted), the provisioning server is required to be configured with (or the operator of a provisioning/management terminal is required to know) the specific service server(s) which is(are) concerned by the data in question, so as to send message(s) requesting the corresponding data modification to the server(s). Moreover, service servers in monolithic implementations usually trend to offer heterogeneous provisioning interfaces, some times being proprietary (i.e. not standardized signaling interfaces). On the other hand, a system arranged according to DLA might offer a single point for data provisioning; namely, the DBS. Furthermore, commercially available DBS products usually offer well-known/standardized signaling interfaces, such as LDAP (“Light-weight Directory Access Protocol”, IETF RFC 4511), which are used by its clients for reading and modifying data stored therein, and which can be used also for data provisioning purposes. These features could help to simplify the provisioning process, diminish the message signaling due to provisioning, and also prevent errors, since the back end DBS of a DLA can provide a single point of access and administration for the data related to a plurality of users. Nevertheless, performing data provisioning directly on the DBS brings about some problems. For example, the server sending provisioning orders (or the human operator handling said server) would be required to predetermine in some cases the impact of a certain data modification on some further related data. In DLA architectures, this has caused provisioning solutions that involved sending first the provisioning orders (i.e. requests to modify some data) to the corresponding front-end(s), and initiating then interactions between the front-end(s) and the DBS so as to store therein the data modification(s) involved by the provisioning order.
Moreover, a characteristic inherent to DLA is that external signaling trend to increase for some servers, as they need to communicate with the DBS for obtaining the data they require to provide their respective services, and also to update these data when needed. Further, since temporary copies of some of these data can be scattered along further service servers (e.g. that keep temporarily copies of the data), more external signaling can be required so as to keep data consistency when some of these data undergo a modification in the DBS. External signaling relies, in addition to the performance of the involved servers, on network elements, such as: routers, bridges, gateways, etc; and also on the bandwidth capacity provided by these elements, which can vary due to other kind of signaling traffic (e.g. not merely due to DLA related traffic), and which can finally affect the performance of the communications system.
It should be therefore desirable to provide solutions that allow, at least partly, diminishing the external signaling in DLA infrastructures, without compromising their inherent benefits.